fix: use stdbuf -o0 cat for unbuffered pipe input, remove debug

- Changed cat subprocess to stdbuf -o0 cat (unbuffered output)
  so characters arrive immediately through the pipe
- Added cat PID to startup messages for diagnostics
- Removed pipe debug logging (trace.log, pipe.log)
- Cat pipe input confirmed working: read-char returns #\a, #\b, #\Newline
- Remaining issue: frame-message format mismatch with daemon
  (pre-existing, not related to input changes)

org/channel-tui-main.org

@@ -912,11 +912,12 @@ Event handlers + daemon I/O + main loop.
         ;; works. A cat subprocess inherits the terminal and provides
         ;; bytes through a pipe that SBCL reads reliably.
         (uiop:run-program '("stty" "-echo") :output nil :ignore-error-status t)
-        (let* ((cat-proc (uiop:launch-program '("cat")
+        (let* ((cat-proc (uiop:launch-program '("stdbuf" "-o0" "cat")
                                               :output :stream
                                               :input :interactive
                                               :stderr nil))
                (tty-in (uiop:process-info-output cat-proc)))
+          (add-msg :system (format nil "* cat pid=~a *" (uiop:process-info-pid cat-proc)))
           ;; Log backend info and terminal dimensions
           (cl-tty.backend:backend-clear be)
           (view-status be w h)